234U/238U disequilibrium in nature: theoretical reassessment of the various proposed models

The 234U/238U disequilibrium observed in nature has been previously interpreted by means of four models based on the properties of α-recoil nuclei and on the transport of uranium isotopes by natural waters. As aqueous dissolution of minerals can potentially dilute such disequilibrium by releasing large amounts of 238U, we tentatively evaluate the ability of these models to quantitatively account for the disequilibrium within different scenarios of aqueous corrosion. We show that three of the models (ejection of recoil nuclei and derived models) require very low (and unlikely) dissolution rates while the last one (change in valence state), which does not depend on the dissolution rates, seems plausible although it has not been particularly emphasized in recent works